The addition of prostate radiotherapy to androgen deprivation may prolong survival in men with newly diagnosed metastatic prostate cancer, according to a study published in Journal of Clinical Oncology.
“Prostate radiotherapy represents an attractive local treatment strategy for patients with metastatic prostate cancer, given its noninvasive administration and broad patient candidacy, advancements in delivery allowing for an increasingly favorable toxicity profile, the established role of radiotherapy in the management of locally advanced nonmetastatic prostate cancer, and recent associations between radiotherapy and improved survival for men with lymph node–positive prostate cancer,” Chad G. Rusthoven, MD, radiation oncologist and assistant professor of radiation oncology at University of Colorado School of Medicine, and colleagues wrote.
Christopher J. Logothetis
The researchers used the National Cancer Data Base to evaluate OS in 6,382 men with newly diagnosed metastatic prostate cancer treated with ADT from 2004 to 2012. Of these, 534 men (8.4%) also received prostate radiotherapy.
Median follow-up was 5.1 years.
Researchers found that the addition of prostate radiotherapy to ADT was associated with a longer median OS (53 vs. 29 months). Further, more men who received radiation in addition to ADT achieved 3-year (62% vs. 43%), 5-year (49% vs. 25%) and 8-year OS estimates (33% vs. 13%; HR = 0.56; 95% CI, 0.50 to 0.64).
Multivariate analysis — stratified for age, year, race, comorbidity score, PSA level, Gleason score, T stage, N stage, chemotherapy administration, treating facility and insurance status — also showed an improvement in OS with prostate radiotherapy (HR = 0.62; 95% CI, 0.55-0.71).
Researchers then conducted a propensity-score analysis of 537 patients who received prostate radiotherapy plus ADT compared with 537 patients who received ADT alone. Resulted demonstrated superior median OS in the radiotherapy group (55 vs. 37 months), as well as better rates of 3-year (62% vs. 51%), 5-year (49% vs. 33%) and 8-year OS estimates (33% vs. 15%; HR = 0.67; 95% CI, 0.57-0.79).
Landmark analysis of long-term 1-, 3- and 5-year survivors showed that the addition of prostate radiotherapy to ADT improved OS in all three subsets.
The magnitude of the association between prostate radiotherapy and improved survival appeared greater in patients with Gleason scores of 8 or less and with T1 to T3 tumors. Age, PSA level and N stage showed no difference.
Patients who received prostate radiotherapy were stratified by dosage, in which improved OS was associated with higher-dose prostate radiotherapy ( 65 Gy) compared with a lower dosage (< 65 Gy).
Rusthoven and colleagues recommended that future randomized trials evaluate the impact of local therapy for men with metastatic prostate cancer.
“Results from this analysis provide a clinical correlation to numerous preclinical studies, suggesting that treatment of the primary prostatic tumor may impact distant disease and potentially improve survival for men with metastatic prostate cancer,” the researchers wrote.
However, the report did not definitively establish the benefit for control of the primary tumor, Christopher J. Logothetis, MD, department chair and professor in the department of genitourinary medical oncology, and Ana M. Aparicio, MD, associate professor — both from The University of Texas MD Anderson Cancer Center — wrote in an accompanying editorial.
“To better integrate the control of the primary tumor into the therapeutic strategy of men with metastatic prostate cancer, optimum local control must be more specifically defined and developed rationally,” they wrote. “More broadly, one can envisage that strategies integrating organ site-specific therapies targeting the prostate and bone metastases will become a component of an effective treatment strategy for men with potentially lethal prostate cancer.” – by Kristie L. Kahl
Disclosure: Rusthoven reports honoraria from ARIAD, AstraZeneca and Clovis Oncology. Please see the full study for a list of all other researchers’ relevant financial disclosures. Logothetis reports consulting fees and/or research funding from Astellas, Bayer, Bristol-Myers Squibb, Johnson & Johnson, Medivation and Sanofi. Aparicio reports consulting fees and/or research funding from Bristol-Myers Squibb, GlaxoSmithKline, Janssen and Sanofi.